selftests/bpf: Refactor timer selftests

Refactor timer selftests, extracting stress test into a separate test.
This makes it easier to debug test failures and allows to extend.

Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20260201025403.66625-5-alexei.starovoitov@gmail.com

Author: mykyta5

tools/testing/selftests/bpf/prog_tests/timer.c

@@ -22,13 +22,35 @@ static void *spin_lock_thread(void *arg)
 	pthread_exit(arg);
 }
 
-static int timer(struct timer *timer_skel)
+
+static int timer_stress(struct timer *timer_skel)
 {
-	int i, err, prog_fd;
+	int i, err = 1, prog_fd;
 	LIBBPF_OPTS(bpf_test_run_opts, topts);
 	pthread_t thread_id[NUM_THR];
 	void *ret;
 
+	prog_fd = bpf_program__fd(timer_skel->progs.race);
+	for (i = 0; i < NUM_THR; i++) {
+		err = pthread_create(&thread_id[i], NULL,
+				     &spin_lock_thread, &prog_fd);
+		if (!ASSERT_OK(err, "pthread_create"))
+			break;
+	}
+
+	while (i) {
+		err = pthread_join(thread_id[--i], &ret);
+		if (ASSERT_OK(err, "pthread_join"))
+			ASSERT_EQ(ret, (void *)&prog_fd, "pthread_join");
+	}
+	return err;
+}
+
+static int timer(struct timer *timer_skel)
+{
+	int err, prog_fd;
+	LIBBPF_OPTS(bpf_test_run_opts, topts);
+
 	err = timer__attach(timer_skel);
 	if (!ASSERT_OK(err, "timer_attach"))
 		return err;
@@ -63,25 +85,10 @@ static int timer(struct timer *timer_skel)
 	/* check that code paths completed */
 	ASSERT_EQ(timer_skel->bss->ok, 1 | 2 | 4, "ok");
 
-	prog_fd = bpf_program__fd(timer_skel->progs.race);
-	for (i = 0; i < NUM_THR; i++) {
-		err = pthread_create(&thread_id[i], NULL,
-				     &spin_lock_thread, &prog_fd);
-		if (!ASSERT_OK(err, "pthread_create"))
-			break;
-	}
-
-	while (i) {
-		err = pthread_join(thread_id[--i], &ret);
-		if (ASSERT_OK(err, "pthread_join"))
-			ASSERT_EQ(ret, (void *)&prog_fd, "pthread_join");
-	}
-
 	return 0;
 }
 
-/* TODO: use pid filtering */
-void serial_test_timer(void)
+static void test_timer(int (*timer_test_fn)(struct timer *timer_skel))
 {
 	struct timer *timer_skel = NULL;
 	int err;
@@ -94,13 +101,23 @@ void serial_test_timer(void)
 	if (!ASSERT_OK_PTR(timer_skel, "timer_skel_load"))
 		return;
 
-	err = timer(timer_skel);
+	err = timer_test_fn(timer_skel);
 	ASSERT_OK(err, "timer");
 	timer__destroy(timer_skel);
+}
+
+void serial_test_timer(void)
+{
+	test_timer(timer);
 
 	RUN_TESTS(timer_failure);
 }
 
+void serial_test_timer_stress(void)
+{
+	test_timer(timer_stress);
+}
+
 void test_timer_interrupt(void)
 {
 	struct timer_interrupt *skel = NULL;